Speaker
Description
Violin modes in the Advanced LIGO (aLIGO) test mass suspension fibers reduce detector sensitivity at their resonant frequencies and pose operational issues when strongly excited. The violin modes are currently measured at the gravitational wave detector readout and are damped via actuation on the penultimate mass. However, the interferometer must be locked to damp the modes with this method, taking away valuable commissioning and observing time. Current damping methods also solely rely on the differential arm length signal for sensing, which limits the ability to resolve violin modes that are close together in frequency. To address these limitations, we are developing an electrostatic violin mode damper (EVMD) consisting of a "split" photodiode and LED integrated into a shadow sensor and an electrostatic actuator. We require our shadow sensor to resolve fiber motion on the order of $10^{-10}\frac{m_{rms}}{\sqrt{Hz}}$, and our actuator to produce an electrostatic force on the order of $10^{-10}N$. We present results for successful damping of a tensioned fused silica fiber in air and strides made toward damping in vacuum, as well as an initial compact prototype design for integration with the aLIGO suspensions.